“We are all so sad to lose him. Everyone loved him. He was a sweet, gentle giant with a big personality. He enjoyed interacting with his caregivers,” said Christina Gorsuch, Cincinnati Zoo’s curator of mammals, in a news release on Tuesday.

The zoo said Henry suddenly lost his appetite. His care team treated his symptoms, but he lost hundreds of pounds. He was weak and disoriented. An animal autopsy will be performed to determine the cause.

“The blood work from Henry’s last exam gave us some hope that he was on the mend, but his appetite never returned and his condition declined rapidly. Vets and his care team worked tirelessly to keep him comfortable and help him fight this illness. Nothing – antibiotics, favorite foods, extra TLC – seemed to turn his condition around,” Gorsuch said.

The 36-year-old hippo arrived at the Cincinnati Zoo’s Hippo Cove in 2016 from Dickerson Park Zoo. He was paired with Bibi and the couple welcomed little Fiona in January.

The baby hippo was born six weeks early and 25 pounds too small. Zoo staff raised Fiona by hand and fed her by bottle until she was healthy enough to join her parents.

“After watching Fiona fight, defy the odds and literally make history, it feels especially unfair and defeating to have to accept this outcome for Henry. While our time with him has been short in quantity, no one can deny that his quality of life before becoming ill was exceptional. From meeting, bonding and breeding with his mate Bibi, to becoming a father to charismatic and spirited Fiona, Henry’s days in Cincinnati were filled with sunshine, watermelons, waterfalls and the highest quality of care that can be provided to any animal,” said Wendy Rice, Africa head keeper.

The zoo said Bibi and Fiona will be fine as a bloat of two, but will notice Henry is missing.

The Cincinnati Zoo said the median life expectancy for a Nile hippopotamus is 35 years.